Image:WW1AcousticMirrorKilnsea(PaulGlazzard)Jan2007.jpg|right|thumb|300px| WW1 concrete acoustic mirror near Kilnsea Grange, East Yorkshire, UK. The pipe which held the "collector head" (microphone) can be seen in front of the structure
An '''acoustic mirror''' is a passive device used to reflect and perhaps to focus (concentrate) sound wave
s. Parabolic reflector|Parabolic
acoustic mirrors are widely used in parabolic microphone
s to pick up sound from great distances, employed in surveillance and reporting of outdoor sporting events. Pairs of large parabolic acoustic mirrors which function as "whisper galleries" are displayed in science museums to demonstrate sound focusing.
Between the World Wars, before the invention of radar
, parabolic sound mirrors were used experimentally as early-warning devices by military air defence
forces to detect incoming enemy aircraft by listening for the sound of their engines. During World War 2...